What's the relationship between `elevation` and `...

# compose

[Marcin Wisniowski]

What's the relationship between elevation and zIndex? They seem to affect each other, but I am not sure how exactly.

[Filip Wiesner]

elevation in the material design refers to the theoretical elevation of the element and the resulting shadow. The zIndex should be purely the draw order in a scope.

[Filip Wiesner]

From shadow() modifier documentation:

Note that elevation is only affecting the shadow size and doesn't change the drawing order. Use a androidx.compose.ui.zIndex modifier if you want to draw the elements with larger elevation after all the elements with a smaller one.